As a first step, we can verify the derived theoretical transmission relation by comparing it with the results presented by Wang at al [1]}. In particular, the Fig. REF  depicts the transmission coefficient of idealized superlens consisting of a single layer of \(\epsilon =-1\)  material, with \(\lambda /10\)  thickness, surrounded by vacuum. There are several characteristic points in the transmission spectrum; for \(k_x/k_0<1\) , the transmitted mode corresponds to regular, propagating wave; the transmission coefficient in this range is smaller than 1. For higher values of \(k_x\) , the transmission coefficient describes evanescent waves that do not carry energy, so one can have \(T>1\) . In particular, the transmission spectrum usually contains two poles [1]}, which are clearly visible on the Fig. REF . For \(k_x/k_0>9\) , there is a cutoff point where the transmission quickly drops. This means that the spatial resolution of the superlens is limited to approximately \(\lambda /9\) ; one can increase this resolution by making the lens thinner [3]}. The presence of the sharp poles in the transfer function (transmission coefficient) is generally undesirable as it introduces distortion [1]}; one can see that the introduction of absorption (Fig. REF , blue line) significantly reduces the gain on the second, high \(k_x\)  pole, so that the transfer function becomes more flat (e.g. all wave modes are amplified to a similar degree). Thus, despite the fact that absorption is in general detrimental to the superlens resolution, its presence can be beneficial to the image quality. Due to this reason, our proposal of Cu-based superlens has some advantages over traditional designs based on noble metals.
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